The present invention relates to medical devices and more particularly to a method and apparatus for measuring the compliance or distensibility of the lower esophageal sphincter (LES) for use in the diagnosis of esophageal function.
It is well known in the art to use esophageal and nasogastric catheters having balloon cuffs to measure the pressure within the esophagus. These devices have been used by and large to study the condition of the lungs and the blood pressure in and around the heart. For these purposes, it is desirous to measure pressure acting on the walls of the esophagus. Accordingly, an elastic balloon cuff, coupled to a suitable pressure transducer via a catheter, is inflated against the esophagus and the amount of pressure resistance is measured and used for various purposes in diagnosis. An elastic balloon is used because it can be distended outwardly to contact and conform with the region of interest in the esophagus.
Physicians also examine the condition of the gastroesophageal junction and in particular the lower esophageal sphincter (LES), which is an involuntary ring-like muscle separating the esophagus from the stomach. The LES rests in a closed position to shut off the end of the esophagus, and is relaxed when in the open state. However, the LES does not have the motility to open on its own, rather it opens briefly by normal physiological function of the esophagus during excitation of the inhibitory nerves of the esophagus. This most commonly occurs during peristalsis when the LES opens to allow food to pass from the esophagus to the stomach. Contracting nerves return the LES to its normally closed position.
Studying the LES is often necessary to diagnose various esophageal maladies and disorders such as gastroesophageal reflux disease, stricture, achalasia, diffuse esophageal spasm, esophageal cancer and dysphagia. These esophageal disorders affect the motility of the LES and thereby its ability to open and close normally.
Motility disorders of the esophagus, including those associated with systemic disease such as that of the connective tissue, are normally diagnosed using manometry, a procedure whereby a pressure-measuring instrument can assess function of the esophageal body by measuring peristaltic presence, propagation and vigor, or nonperistaltic contractions, as well as that of the upper and lower esophageal sphincters by measuring resting tone, timing and completeness of relaxation, and response to exogenous stimuli. The use of manometry is especially indicated in cases where more common esophageal disorders have been excluded after a barium radiograph or endoscopy evaluation, and it is often indicated for preoperative assessment of peristaltic function prior to antireflux surgery, and for placement of devices when the location depends on functional landmarks such as the lower esophageal sphincter (LES) located at the esophageal and gastric junction.
To obtain manometry data, the clinician typically measures the pressure exerted by the LES when constricted as well as when it is relaxed. This is typically done manometrically by inserting a sleeve with pressure transducers or other pressure recording devices into a patient""s LES and measuring pressure as the patient swallows. The constricted and relaxed pressures are then compared to known values for a healthy LES (approximately 15-30 mm Hg constricted and 1-5 mm Hg relaxed). An LES with abnormal pressure values is then treated with drugs or a surgical procedure. A problem is that the measured pressure values of an LES may be normal despite the existence of dysphagia with or without an esophageal dysfunction. In this case, measuring the LES pressure does not provide information helpful in making a diagnosis. An additional disadvantage of manometry measurement is that it is a highly technical procedure that requires significant knowledge and precise methodology to produce valid results. Therefore, it has tended to be used more for physiological studies rather than a diagnostic tool in endoscopic or radiographic procedures. For example, manometry alone is insufficient to diagnose compliance disorders of the LES; the compliance of a sphincter is its ability to stretch and open properly in response to pressure applied to it from within to regulate the flow or movement of liquid or solid materials therethrough. For example, an important function of the LES is to prevent reflux of stomach acid into the esophagus, which not only causes discomfort to the sufferer, but can lead to a potentially serious condition known as Barrett""s Esophagus. The ability to determine the degree of LES compliance is especially important during surgical procedures such as Nissen Fundoplication which involves wrapping the fundus of the stomach around the lower esophagus and suturing it into place to augment the biomechanical function of the LES. A quantitative measurement of compliance can provide an indication of whether the wrap is too loose or too tight, the latter resulting in an increased LES stricture that could cause difficulty in swallowing. If LES compliance can be assessed intraoperatively, the wrap can be adjusted, preventing the need for a second procedure to correct the problem. What is needed is a device that can be easily and reliably positioned for measuring compliance of the natural or reconstructed LES or gastroesophageal junction and to provide reliable data that can be readily interpreted to produce a quick assessment.
The inventor of the present invention has determined that, rather than the pressure exerted by the LES, the compliance (or distensibility) of the LES is determinative in diagnosing the LES dysfunction in certain medical and surgical cases. Simply measuring the pressure exerted by the LES is insufficient because it is possible for a dysfunctional LES to have proper pressure values due to the tone of the LES muscle, despite having abnormal compliance. Thus, to perform a useful diagnosis, it is necessary to isolate compliance from muscle tone, which can only be done by relaxing the LES and changing its diameter in a controlled manner to detect the change in pressure that is needed to change the LES diameter. However, as mentioned above, the LES is ordinarily constricted, relaxing only briefly to allow passage between the esophagus and stomach.
The foregoing problems are solved and a technical advance is achieved in a method and apparatus for maintaining the LES in a relaxed state and measuring the compliance of the LES in vivo. According to the invention, the LES is relaxed by distending the esophagus at a suitable position above the LES with a first extendable member, such as a balloon. The balloon is inflated to relax and trigger motility of the esophagus, thereby simulating a natural swallowing response that permits measurement the amount of resistance provided by the LES without the underlying tonic interference. As a result, a pressure reading can be obtained which is a more clinically relevant measurement of the compliance of the LES.
To measure compliance of the LES, a second extendable member, such as a non-elastic or non-distensible balloon (or bag), is inserted within the LES and filled at prescribed air volume increments via a catheter. A non-elastic balloon is infinitely compliant in that the pressure inside will not change until the volume of air being introduced into the balloon is at least equal to the volume of the balloon upon fabrication. The pressure within the bag is measured by a suitable gauge at each change in volume. A volume/pressure curve and/or data table is generated. These data can then be compared to established compliance norms for making a diagnosis. The pressure is measured by a measurement device, such as a gauge or pressure meter, reading the inflation lumen communicating with the non-elastic (intrasphincteric) balloon. By repeated inflations of the esophageal balloon using increasing volumes of air to obtain an increased physiologic response, a volume vs. pressure curve can be established for a particular patient that allows assessment of whether the LES is functioning properly. An alternative method of measuring pressure is to include a manometric pressure (recording) port within the intrasphincteric balloon that communicates with manometry sensors and transducers that are typically located at, or connected to, the proximal end of the compliance measurement catheter. While the extendable members of the present invention are typically balloons, they can assume any configuration (e.g., a basket) that can be manipulated to either obtain a pressure reading within the LES or extend outward to stimulate the esophagus to elicit the correct physiological response by sphincter.
In one aspect of the invention, the first and second balloons are mounted to an elongate member such as a surgical catheter defining a plurality of lumens. The first and second balloons are located along the catheter such that the intrasphincteric balloon is positioned in the LES (or gastroesophageal junction), while the first balloon is positioned in the esophagus. The lumens of the catheter communicate with an actuating mechanism or inflation means, such as a suitable air pump or syringe, and an apparatus for measuring pressure, such as a standard pressure gauge. The catheter lumens suitably terminate at ports within the bag and balloons, for filling the bag and balloons and measuring the intra-bag pressure.
In another aspect of the invention, the compliance balloon catheter further includes a distal, gastric balloon made of a compliant or non-elastic material that is inflated within the stomach so that the catheter can be partially withdrawn until the gastric balloon lodges below the LES, thereby correctly positioning the intrasphincteric balloon within the LES.
In still another aspect of the invention, manometric pressure ports are located at one or more points along the compliance balloon catheter for reading pressures found within the gastrointestinal tract. By comparing readings against known pressure gradient values that occur at various points within the esophagus and stomach, the compliance balloon catheter can be placed with some precision.
In still yet another aspect of the invention, a method for placement and use of a compliance balloon catheter in the LES is described in which the device is placed either transnasally or orally, and with or without the use of an endoscope. Referring to an embodiment that includes a gastric balloon, the compliance balloon catheter, preferably with the balloons deflated, is advanced such that at least the distal portion (defined herein as that portion of the catheter extending beyond the intrasphincteric balloon) is within the stomach. The gastric balloon is inflated and the catheter is partially withdrawn until the gastric balloon abuts the stomach wall and comes in contact with the LES. While the position of the compliance balloon catheter is maintained, the intrasphincteric balloon is inflated to determine baseline LES compliance. The esophageal balloon is then inflated. This balloon applies outward pressure on the esophagus at a suitable position above the LES, which causes the LES to relax through natural physiological functioning of the esophagus. To establish a volume-pressure relationship for evaluating sphincter compliance, the esophageal balloon is inflated with a series of increasing volumes of air and the resulting pressures produced by the sphincter acting upon the balloon are read by a pressure gauge attached to the inflation lumen of the intrasphincteric balloon, or by a manometry sensor and transducer attached to another catheter lumen separate from the intrasphincteric balloon inflation lumen. The data are used in a plot of volume vs. pressure with the slope of the curve providing an indication of LES compliance. This relation can then be compared against that of normative standards in making a diagnosis of the condition of the LES. After the final reading by the intrasphincteric balloon, all three balloons are deflated and the device is removed from the patient. The intrasphincteric balloon can be least partially deflated or maintained at the current inflation volume in between the series of inflations.
The intrasphincteric balloon can also be positioned within the LES manometrically. In this case, the catheter will include additional lumens terminating at ports located outside of the balloons. This allows the pressure at various locations within the esophagus to be measured and used to properly locate the balloon within the LES. Manometric measurements also can be used in combination with the gastric balloon for verification of correct placement.
Thus, the present invention provides a means for measuring in vivos the compliance of a relaxed LES. The pressure within the bag at various stages of inflation can be measured to establish a relation between volume and pressure. Predisposing the LES in a relaxed state removes the tension and tone of the muscle and allows the LES to distend without restriction from the muscle. This allows the compliance of the LES to be measured irrespective of muscle tone. Ultimately, this provides for a more effective means to diagnose certain esophageal dysfunctions.
Other objects and advantages will become apparent from the following description and drawings.